Tunnel kiln



Sept.` 27, 1927.

1,643,775 .1. KELLEHER TUNNEL KILN Filed Aug. 29,Y 1925 Patented Sept. .27, 1927.

UNITED STATES 1,643,775 PATENT OFFICE.

JAMES KELLEI-IER, OF CHIPPAWA, ONTARIO, CANADA, ASSIGNOR T HARPER ELEC- TRIC FURNAGE CORPORATION, A CORPORATION 0F NEW YORK.

TUNNEL xILN.

Application filed August 29, 1925. Serial No. 53,284.

This invention relates to furnaces, and the particular embodiment herein disclosed shows its application to tunnelkilns wherein material or articles to be heat-treated are passed through a tunnel, the parts of which.

are heated to the required temperatures. In tunnel kilns for firing ceramic ware, heattreatment of steel, reduction of ores and other kindred uses, different gases in differf ent parts of the tunnel are often required. For firing porcelain,'for example, at lower temperatures, a strongly oxidizing atmosphere may be required,v during the process of actual firing a reducing atmosphere, and during the cooling down a strongly oxidizing atmosphere. My invention provides for an improved method whereby` one, two or more different gases maybe kept `within definite, limits throughout the tunnel of the .furnace without any .substantial commingling. A. Y l

Numerous objects and advantages of my invention will appear from the following description, taken in connection with the accompanying drawing, wherein- Fig. l represents diagrammatic'ally `a kiln tunnel with means for supplying gases thereto. v

Fig. 1A is a diagram indicating the pres sures of the gases at various points along the length of the tunnel shown in Fig. l.

Figs. 2 and 2A are similar to Figs. l and 1A respectively but showing a modified form of my invention, 'and Figs. 3 and 3A are similar to Figs. l and lA respectively but showing a further modification. .Y

Referring to F igs.V 1, 2 and V3,' reference character l represents the walls of the tunnel and reference character 2, the space in- 40 side the tunnel. For the purpose of explaining the application of my invention to theform shown in Fig. l, let it be assumed that between the points Mv and N in the tunnel space a reducing atmosphere is required, between the point M and the end of the kiln to the left and between the point N and the endof the kiln to the right, an oxidizing atmosphere is required. AReference characters 3 and 4L represent fans or exhaust blowers, and 5 a storage reservoir for carbon monoxide or a carbon monoxide gas 'producer. When the fan 3 yis connected to the tunnel by the'pipeB and exhausted into the pipe C,y both 'ofwhich pipes connect with the interior of the tunnel as shown, a'stream of air sucked in from the'left-hand end of the tunnel will ilowas indicated by the arrows c, b, c and d. e Fig. 2A indicates diagrammatically the pressures at various points in the tunnel, the line 6 representing 50 normal atmospheric pressure. Line 7 represents the pressure in the tunnel from the inlet at the left to the point at which the pipeB connects with the tunnel, and shows a gradual decrease in pressure below atmosl55 pheric. Line 9 represents the pressure in the tunnel -at the right of the point at which the pipe C connects therewith, and shows a pressure above atmospheric and gradually decreasing to atmospheric pressure lat the kright end of the tunnel. lf no means were employed "for preventing the flow yof air toward the left from N to M, there would be a circulationof air in the 'tunnel from the outlet of pipe C to the inlet of pipe B. By proper regulation of the i'low of carbon monoxide from the reservoir 5 through pipe Gr, thence through the tunnel as indicated at to. the inlet to pipe E and thence to and through the blower' 4, so that the pressures of the air and gas at the portion Nin the tunnel are substantially equal and the pressures of the air and gas at the portion M aresubstantially equal. l am able to separate they streams of air.. and carbon monoxide and prevent any substantial connnin gling of these gases. The pressures of the carbon monoxide along the tunnel from M to N are indicated by the line 8 inA Figf'lA, and it will be noted that the pressure of 9L, the carbon monoxide at the point M is sub-V stantially equal to the pressure of the air at the point M, and that the pressure of the carbon monoxide at the point N is substantially equalto the pressure of the air at the point N. f

Referring to Fig. 2, the blower 3 draws in air from both endsof the furnace tunnel along paths a and d tothe points M and N respectively. The air Vthen passes along parallel paths through pipes l5 and lll tothe blower 3 and is ldischarged to the atmosphere through pipes I., The blower or fan l discharges through the producer 5 and through the pipe c to a point in the tunnel vapproximately midway between the points M and N, whence the gas flow divides and passes through the tunnel in opposite direc- Los ' tions, as indicated atv f', to the points M and pipes L. The pressures in the tunnel are indicated in Fig. 25 and it will be seen that the pressure drops from atmospheric pressure at the left hand end of the tunnel to the point M, as indicated by the arrow 14. Similarly, the pressure from the right hand end ot the tunnel drops from atmospheric pressure to the point N, as indicated by the arrow 16. Between the points M and N the pressure rises to the point 17 which represents the pressure in the tunnelat the outletot' the pipe K. lt will be noted in Fig. 2 as well as in Fig. l that the pres-y sures of the air and carbon monoxide at the point- M are substantially equal, and this is likewise true at the point N. It will also be noted that at the point M the air and carbon monoxide are moving` in opposite directions through the tunnel, and this is lihewise true at the point N.

oit the two streams at adjacent points and the `motion ci' the gases in opposite directions at these points, serve to etectually prevent any substantial eoinmingling of the gases. Y

lFig. 8 represents a system similar to lthat shown in li'ig. 2, the principal difference being that by heating thek cold air'u during `the passage along the tunnel at a to the point M this air may be employed to heat up any ware entering the tunnel at the right and moving toward the point N.V rllhis is accomplished by exhausting lthe gases from the fan 3 into the tunnel at the right hand end and causing them to passtoward the lett through the tunnel, as'indicated at d, to thepoiiit N, whence they are exhausted through the fan 10 into the atmosphere.v

'ihe pressures at'various points inl the tunnel are shown in Fig. 3^. cold ware'as 1t passes into 4the tunnel by means or' heated gases may be utilized" inV the construction shown in'Fig. 1, wliereit will be seen that Vit' the ware enters the tunnel from the right hand end it will be exposed to the'heat ot the air which has paseedlthrough the'tunnel atthe left hand' end, thisv air beingk heated by contact'with the heated ware as it passes through the left hand end ot the tunnel.

This method of controlling various gases and gas mixtures in various parts ofthe tunnel' or chamber may, ot course,lbe varied by pressure gauges, as shown diagraminati' cally at 2O in Fig. l, and the control of the pressures in the various parts of the tunnel These two condi-y tions, nan ely, the equality of the pressure4k yifhe heating ot ,thel

may be effected by control of the blowers orby valves such as are indicated diagrammatically at 2l in Fig. l. VYhen the heating of cold ware by heated gases isl desired, l pieter the forms ot my invention'hdisclosed in Figs. l and 3. Where, however, this'heating is notot great import, the form shown in liig. 2 is preferable. Vhile have shown fans or. blowers as a means for inducing the draught, chimneys or other draught-inducing appliances-may be use-d. it will be understood that the rate of change in the pressure from point to point of the tunnel, which is indicated in Figs. lA,-2A and gaby the angles which the pressure lines malte with thedatum line 6, may be varied without departing from thel spirit ot" the invention. Y

Vlclaiin: l l. The method of operating a tunnel kiln which comprises causing a stream of gas to enter the tunnel 'under pressure so as to substantially lill a portion of the tunnel, withdrawing said gas at another point -o-lsaid tunnel-at a pressure below atmospheric, ad-

niitting another gas to the tunnel so as to substantially lill another portion of the tune nel, and withdrawing said second gas adjacent the point ot'jwithdrawallof said irst gas.

and atI substantially the same pressure below atmosphere said gases being in contact with each other adjacent'ftheir/point of .withdrawalb- 2. The method of operating a i tunnel :kiln

which comprises substantially filling adj acent portions of the tunnel withan oxidizing gas and-.a1 non-oxidizing gas respectively Vin contact with each other at a predetermined pointV maintaining a supply` oi eachxot rsaid gases to their respective portions of the tunnel, and withdrawing each of saidV gases Vat a point adjacent to 'said point ot'contact between said-gases. i

8.. The .method of .operating altunnel kiln which comprises substantially-filling adjace-V ent portions of .the v.tunnel withan oxidizing and a reducing gas respectively, maintaining said gases in directcontactwith each other.- at a predetermined. point,v and withdrawing gas lfrom'said tunnel adjacent saidy point ofwithdrawal so as to causea flow of fresh gas; i toward said. point. A i

4L., The method lof loperating atunnel kilnv which comprises substantially filling diii'erent portions ofthe continuous tunnel withV an oxidizing and a reducing gas respectively-,

said tunnel portions being in openrcommu'nication with eachotherl as portions of the same continuous ltunnel p.assage,and` withdrawing gas from eachv of :said portions so as to causea flow of fresh' gas in each portion, the materialpassing through the kiln! being subjected to said oxidizing and reducing gases at diier'ent times. v

Themet-hod of operatinga tunnel kiln i the ends of said portion, and the pressure of the reducing gas at each end of said intermediate portion being substantially the saine as the pressure of the oxidizing gas adjacent said end. l

6. The method of firing ware in a tunnel kiln which comprises causing air to pass through a portion of the tunnel adjacent one end and be exhausted through a portion of the tunnel adjacent the other end, causing a reducing gas to flow through a portion of said tunnel intermediate said first named portions, maintaining a substantially uniform pressure in 'the tunnel at the portions thereof where the aii and gas are adjacent to one another, and passing the -ware through the tunnel from the second mentioned end of said tunnel to the first mentioned end, whereby air which has been heated by outgoing ware serves to heat the ingoing ware.

7. The method of operating a tunnel kiln which comprises drawing air into opposite ends of the tunnel and causing the air to How through portions of the tunnel adjacent said ends, introducing a reducing as into said tunnel approximately midway etween said portions and exhausting'said reducing gas fromy said tunnel at points adjacent said portions.

8. The method of operating a tunnel kiln which comprisesdrawing air into opposite ends of the tunnel and causing the air to flow through portions of the tunnel adjacent said ends, introducing a reducing gas into saidv tunnel approximately midway between said portions, exhausting said reducing gas' from said tunnel at points adjacent said portions, and maintaining the pressure in said tunnel substantially uniform along the portions of said tunnel where the gas and air are adjacent to one another.

JAMES KELLEHER. 

